Is It Permissible to Celebrate a Bar Mitzvah During the Three Weeks?

Hello, 

It is permitted to celebrate a bar mitzvah during the Three Weeks, and according to the view of Rabbi Ovadia Yosef zt"l it is also permitted to play musical instruments (Responsa Yabia Omer, part 6, siman 34). And if the bar mitzvah falls in the week in which Tishah B'Av occurs, even the bar mitzvah boy is forbidden to get a haircut; however, he is permitted to wear Shabbat clothing, but not completely new clothing (Chazon Ovadia, Four Fasts, p. 224). It is permitted to eat meat and drink wine at the seudah held in honor of the bar mitzvah on the day he completes thirteen years and one day. However, if his thirteenth birthday falls on the eve of Tishah B'Av, it is best to delay the seudah until after Tishah B'Av (ibid., pp. 174-175). 

Blessings, 

Hillel Meirs